class Partition {
public:
    typedef struct ListNode Node;
    ListNode* partition(ListNode* pHead, int x) {
        Node* head1, * head2, * tail1, * tail2;
        head1 = tail1 = (Node*)malloc(sizeof(Node));
        head2 = tail2 = (Node*)malloc(sizeof(Node));
        tail1->next = NULL;
        tail2->next = NULL;
        Node* cur = pHead;
        while (cur)
        {
            if (cur->val < x)
            {
                tail1->next = cur;
                tail1 = tail1->next;
            }
            else
            {
                tail2->next = cur;
                tail2 = tail2->next;
            }
            cur = cur->next;
        }
        tail1->next = head2->next;
        tail2->next = NULL;
        pHead = head1->next;
        free(head1);
        free(head2);
        return pHead;
    }
};